The present invention relates to a driving tool for driving fastening means into a workpiece and to a method for operating such a driving tool.
The driving tool in question is used primarily as a handheld tool, for example for fastening particle boards on supporting structures. The term “fastening means” should be understood here in a broad sense and comprises not only nails and staples but also screws, pins or the like. The main focus of attention here is on the driving in of nails, which should not be understood as being restrictive.
The fastening means usually take the form of a magazine belt. Depending on the design, the magazine belt may for example have a carrier belt of plastic or metal, which carries the individual fastening means. Another variant is that of providing a series of parallel running fastening wires, which are tacked on to the individual fastening means.
The driving tool in question may be designed as a compressed-air-operated driving tool, as a combustion-powered driving tool or as an electrically operated driving tool or the like.
The known driving tool (U.S. Pat. No. 6,604,664 B2), on which the invention is based, is designed as a compressed-air-operated driving tool. It is provided with a pneumatic actuator unit, which serves for driving in the fastening means in individual driving-in cycles.
For triggering the driving-in cycles of the pneumatic actuator unit, a triggering assembly is provided, having a trigger lever that can be actuated manually and a workpiece contact element that can be actuated by placing the driving tool onto the workpiece.
What is advantageous about the known driving tool is the fact that it can be operated in two different operating modes. In the single shot mode, each individual sequence of an actuation of the workpiece contact element (from the unactuated state of the workpiece contact element) with subsequent actuation of the trigger lever (from the unactuated state of the trigger lever) triggers a driving-in cycle. In the bump firing mode, with the trigger lever continuously actuated, each individual actuation of the workpiece contact element (in each case from the unactuated state) triggers a driving-in cycle.
In the case of the known driving tool, a resetting from the bump firing mode into the single shot mode is provided in an automatic, time-controlled resetting operation. For this, the driving tool has a resetting assembly with a control volume. The resetting assembly can be activated in the bump firing mode, by air at a working pressure being admitted into the control volume. The control volume is provided with an air-venting opening, which allows slow venting of the air. If the pressure goes below a limit value, this has the effect after a predetermined delay time of transferring the driving tool into the single shot mode. A separate valve, the valve piston of which is coupled to the workpiece contact element, is provided for the activation of the resetting assembly. An actuation of the workpiece contact element consequently leads to an activation of the resetting assembly. This is intended to achieve the effect that, when the driving tool is not used over a certain delay time, there is a correspondingly automatic, time-controlled resetting of the driving tool from the bump firing mode into the single shot mode in a resetting operation.